I read yesterday of a local man who said that he had been stopped by the police and ordered to appear at Court in the morning.
He said that he had drunk two drinks over a course of several hours with food and had driven home.
He was very surprised that he had been ordered to appear in Court (where he will almost certainly receive a large fine).
The legal limit in Spain is 0.25 mg/l or if you are a professional driver (bus, taxi, for example), or a learner driver it is reduced to 0.15 mg/l, or someone who has passed their test less than 2 years ago.
Remember that if you drink on an empty stomach the alcohol will be absorbed much quicker and it is hard to say how much you can safely drink as it varies considerably for different people, weight, build, etc. Obviously, the safest thing is not to drink at all and drive.
If you do, be very careful, as now in the Summer is the time that police are at their most vigilant.